英文:
What is the use of @Self() resolution modifier in Angular?
问题
Angular文档中提到Self是“用于构造函数参数的参数装饰器，告诉DI框架从本地注入器开始解析依赖关系”。
如果我有一个组件如下所示
@Component({
selector: 'app-foo',
templateUrl: './foo.component.html',
styleUrls: ['./foo.component.scss'],
providers: [BarService],
})
export class FooComponent {
constructor(public barService: BarService) {}
}
尽管我在根注入器中提供了BarService，但FooComponent将注入自己的服务实例，因为它在组件的提供者列表中。而且它可以在没有@Self() 的情况下工作。
显然，我缺少了一些东西，因为我无法想象在哪种情况下可以使用@Self()。
我已经阅读了很多关于解析修改器的文章，但仍然不清楚@Self() 的用例是什么。
英文:
Angular docs say that Self is Parameter decorator to be used on constructor parameters, which tells the DI framework to start dependency resolution from the local injector.
If I have a component like this
@Component({
selector: 'app-foo',
templateUrl: './foo.component.html',
styleUrls: ['./foo.component.scss'],
providers: [BarService],
})
export class FooComponent {
constructor(public barService: BarService) {}
}
Though I provided BarService in root injector, FooComponent will inject its own instance of service because it's in the Components providers list. And it will work without @Self().
Clearly, I'm missing something because I can't imagine in which scenarios @Self() can be used.
I've read numerous articles on resolution modifiers but still, it is not clear to me what are the use cases of @Self()
答案1
得分: 1
@Self() 表示组件需要提供自己的实例。
当你使用 @Self 时，即使根注入器有一个引用，如果组件没有提供自己的服务实例，就会抛出异常。
这是为了确保实例不依赖于父级。
英文:
@Self() means the component need to provide it's own instance.
When you have @Self, even if the root injector has a reference, an exception will be thrown is the component doesn't provide its own instance of the service.
This is to ensure that instance does not depend from the parents.
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